Hi rkudyba
As you have a support request open for this, we will work on the issue there.
However, for the benefit of the community, you may check the cm-upgrade.log file to determine the reason the upgrade failed.
On the headnode (if upgrading the headnode):
/var/log/cm-upgrade.log
Inside a software image on the headnode (if upgrading a software image):
/cm/image/<your-image>/var/log/cm-upgrade.log